System Architecture of the IPEI Payload on ROCSAT-1


The Ionospheric Plasma and Electrodynamics Instrument (IPEI) is one of the three payloads on the ROCSAT-1 satellite. The IPEI consists of two major packages: Sensor Electronics Package (SEP) and Main Electronics Package (MEP). The SEP carries four sensors: an Ion Trap (IT), Horizontal and Vertical Drift Meters (HDM and VDM), and a Retarding Potential Analyzer (RPA). These sensors measure ion concentration, ion temperature, cross-track ion velocity, and major ion composition at the satellite position along the ROCSAT-1 orbit. This will nominally yield coverage at 600km altitude within the latitude band of ¡_35¢X. The MEP contains four major parts: a digital processing unit (DPU), command interface, science data interface, and power supplies. The MEP provides the electrical interface between IPEI and the spacecraft. Also, the MEP implements the operational modes of IPEI: NORMAL, FAST, and AUTO. In the NORMAL mode the IT, HDM, and VDM provide measurements of the total ion concentration and the cross-track ion drift velocity at 32 Hz, while the RPA provides the in-track ion drift, the ion temperature and the major ion composition at a nominal 1/2 Hz rate. In the FAST mode these sample rates are 1024 Hz and 1/4 Hz respectively. The AUTO mode enables IPEI to switch from the default NORMAL mode to the FAST mode when sudden large changes in the ion concentration, commonly associated with plasma structures called bubbles, are detected. The unique feature of the AUTO mode allows the scientists to investigate spatial structures with scale sizes as small as 16 meters.

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